Many people are concerned with the degree of pigmentation of their skin. For example, people with age spots or freckles may wish such pigmented spots to be less pronounced. Others may wish to reduce the skin darkening caused by exposure to sunlight or to lighten their natural skin color. To meet this need, many attempts have been made to develop products that reduce the pigment production in the melanocytes. However, the substances identified thus far tend to have either low efficacy or undesirable side effects, such as, for example, toxicity or skin irritation. Therefore, there is a continuing need for new skin lightening agents, with improved overall effectiveness, as well as agents that lend themselves to ease of processing in their manufacture.
Resorcinol derivatives have cosmetic skin and hair benefits. Certain resorcinol derivatives, particularly 4-substituted resorcinol derivatives, are useful in cosmetic compositions for skin lightening benefits. Resorcinol derivatives are described in many publications, including U.S. Pat. No. 4,959,393; Hu et al., U.S. Pat. No. 6,132,740; Bradley, et al., U.S. Pat. No. 6,504,037; and Japanese published patent applications JP 2001-010925 and JP2000-327557. Resorcinol derivatives are known compounds and can be readily obtained by various means, including by a method wherein a saturated carboxylic acid and resorcinol are condensed in the presence of zinc chloride and the resultant condensate is reduced with zinc amalgam/hydrochloric acid (Lille, et al., Tr. Nauch-Issied. Inst. Slantsev 1969, No. 18:127-134), or by a method wherein resorcinol and a corresponding alkyl alcohol are reacted in the presence of an alumina catalyst at a high temperature of from 200 to 400° C. (British Patent No. 1,581,428). Skin lightening compounds that may be derived from coumarin are disclosed in Applicants' co-pending patent application Ser. No. 10/227,642 filed Aug. 23, 2002. Some of these compounds can be irritating to the skin.
Applicants have now discovered that the use of compounds that which may be derived from coumarin derivatives (although not limited to such process), deliver skin lightening benefits. The general chemical formulas and structures of these compounds are discussed in more detail herein below. Hydroxy coumarin derived compounds, and especially 4-substituted 7-hydroxy-coumarin derived compounds which resemble resorcinol derivatives, have been found to be effective and possibly less irritating to the skin and are relatively simple to manufacture. These compounds are referred to herein as “coumarin derived resorcinol derivatives.” Coumarin derived resorcinol derivatives of the present invention have not been used for personal care or, in particular, for lightening skin.